Sadly, the only good time is between 2 am and 4 am. I am not kidding. So, for example, if you head south into LA on the 5 at 1 pm, you will sail all the way to the 134 and then will usually crawl from there to the 605.
If you don't want to travel in the middle of the night, your best bet (from either direction) is to approach LA at around 10:30 am -- you will be clear of the mess around 1:30 pm.
On weekends, earlier in the day is always better. You'd think weekends would be lighter, but nope. The traffic is shifted to the afternoon and evening, but still lots and lots of cars.
If you do travel at 2 am, be aware that the bars close at that time, so watch the drunks. The good news is that everyone is texting all the time, so everyone drives like a drunk all the time.
If this sounds a little apocalyptic, it is. I live here. And until recently, I have been commuting back and forth to LA on the 5 for 30 years.
And when we drag our trailer through LA, and DW won't tolerate a 3 am trip, I leave the house at 10 am and hope for the best.
One more tip -- on the southbound 5, just after the 10 interchange, watch your lane selection -- it is easy to get shunted off onto the wrong freeway at that point if you are not paying careful attention to the signs.